The theme of this project concerns the relationship between membrane transport of ions and the role of ions in the regulation of metabolic activity. The specific purpose of this study is to investigate the function of the plasma membrane of the Ehrlich mouse ascites tumor cell in the control of inorganic phosphate transport and the relationship of this transport to the metabolism of phosphate. Since inorganic phosphate participates in energy metabolism and thereby differs from other inorganic anions, regulation of phosphate transport can be considered to be part of the general problem concerning the mechanism of permeation of other biologically important anions. Therefore, we plan to investigate the role of membrane factors (surface charge density, electrical potential difference), as well as environmental factors in the regulation of anion transport. Through these efforts, we anticipate a more complete understanding of the molecular events associated with the transport of phosphate and, indeed, other inorganic anions. Knowledge of the regulation of phosphate transport and metabolism, and its relation to metabolic control in tumor cells hopefully will provide greater insight into the central biologic problem of metabolic control. BIBLIOGRAPHIC REFERENCES: Levinson, C. and Villereal, M.L. The transport of sulfate ions across the membrane of the Ehrlich ascites tumor cell. J. Cellular Physiol. 85:1-14, 1975; Levison, C. Chloride-induced sulfate efflux in ascites tumor cells. Fed. Proc. 34:328, 1975.